Refridge Recharge

[fourlyons]

Originally Posted by djousset

So green is the high pressure side valve and yellow is the low?

Correct.

If you believe it's low on refrigerant and don't have gauges, you can get a charging hose with a tap to install on a R134 can. However your unit has the older R12 Schrader valves, not the newer R134 automotive style valves. You need a can of R134 and a charging hose with an old style R12 connector. There are also adapters you can get to put on your valves that converts them to accept a R134 hose connector. Charge hoses with the R134 connection are easier to find, at least in the States.
Then, just give the fridge a brief shot of refrigerant and wait to see how much of the evaporator frosts up. Ideally you start with a warm fridge, turn it on and check how much of the evaporator frosts up. If it's only partial, turn it off, let it warm up, then give it a shot. Restart the fridge and check how much frosts up. Continue until all of the evaporator frosts up but not the line returning to the compressor.
These units hold very little refrigerant and are super sensitive to the correct charge amount. Too little or too much and they don't cool. According to the spec sheet and depending on which version you have, it's somewhere between 6 and 8 1/2 ounces.
Again, this all assumes the unit cycles but the evaporator doesn't or only partially frosts up, and no air has found it's way into the system. That is unlikely if it does frost some.

[Bellinghamster]

You say it cycles often. That could be the controller or the thermostat (even though it's new). If you jumper across the thermostat terminals on the controller, it should turn on the compressor and keep running indefinitely. If it cycles off then yes, likely a problem with the controller and adding refrigerant won't help.

Also, you should check the current draw when it's running. A 12V Danfoss BD50 compressor should draw around 5 amps (plus fan current). If less, its likely undercharged. If more, it could have a restriction (like blocked capillary tube) causing too much head pressure (high side pressure) in which case adding additional refrigerant won't help.



If thinking of adding refrigerant,first let it run for awhile (like 15 minutes, thermostat jumpered or set to lowest temperature) and watch compressor current and frost line on the evaporator, or better, use an IR gun thermometer to measure the evaporator pathway temperature to find where the path transitions from cold to warmer. Trace the path from where the little tubing (the cap tube) is crimped, the "inlet". That should get cold first, then progress towards where the larger (1/4") tube exits to the suction line to the compressor. It can take quite awhile for the system to stabilize, and the "cold" line will gradually move along the evaporator maze from the input to the output as it does. Ideally, you want almost all the evaporator pathway to be cold (for reference mine runs about 12F while I'm doing this with the box lid open). If only part of the evaporator gets cold while the compressor runs continuously and amp draw is under 5A you'll want to try adding some refrigerant.

There are all sorts of "best practices" to make sure you don't get any air in the system - like making sure the charging hoses are purged, bleeding a bit of refrigerant while you make the connection. Ideally charging is done through an HVAC gauge manifold you first purge then connect to the suction side when the compressor is off to make sure it won't have a vacuum on the suction side and pull in air when connecting the hose to the service port... recommend watching some videos or asking an HVAC tech to help and teach).

A small can of R134A and corresponding can valve (ideally the kind with a self-sealing valve in the can) can be purchased at most automotive parts suppliers (Napa, Oreilley's, Autozone, etc.), although some states have banned sales to anyone who doesn't have a refrigeration tech license. You want pure 134A, no oil, no leak-stop, dyes, etc. Then you need a charging hose that fits the can valve and a 1/4" flare fitting. Make sure the flare connector end has a shrader valve depressor (piece in the middle of it to push the valve in the service port down when it's connected).
Connect the valve to the can, connect the hose to the valve.

Connect the other end of the hose "loosely" to the service port (not depressing the schrader valve). With the can upright (so it is expelling vapor, not liquid refrigerant) screw the valve handle in slowly to open the valve until you hear refrigerant starting to flow out the hose (this purges the air out of the hose), then back the can valve out until flow stops and immediately tighten the hose to the service port. You're now ready to add charge to the system. If you have an accurate scale, set the can on it and zero the scale (the hose will screw with your reading... do the best you can). Turn on the compressor, let it run for awhile to "pump down" the low side pressure so it can draw refrigerant from the can. Again with the can upright turn the can valve handle in so refrigerant flows very slowly (this is where the HVAC gauge manifold make things a lot easier!). Add a tiny bit (like 1/2 oz) of refrigerant slowly then back off the can valve to stop the flow and let the system run until the new "frost line" on the evaporator is determined (like 10-15 minutes). Repeat adding a little bit at a time and letting it "settle" until almost the entire evaporator is cold. While doing this, watch compressor current. If it goes up over ~5.25A stop charging and wait to see if it comes down. If it drops under 5A continue adding refrigerant per the frost line. If it stays above 5A then stop adding, close your refrigerator lid and let it run awhile to cool down the box (and evaporator). Properly "tuning" the charge can take a couple hours even if you know what you're doing. Patience!



You don't want to get any air into the system!
You don't want to feed liquid refrigerant into the suction side of the compressor
You don't want to release refrigerant (screw in and unscrew the hose to the service port quickly, make sure you're can valve is backed out before disconnecting the hose from the service port.

[djousset]

@fourlyons and bellinghamster

Thanks for the diagnostic suggestions and good detail on the recharge.
I'll give it a try.

[fourlyons]

Originally Posted by djousset

@fourlyons and bellinghamster



Thanks for the diagnostic suggestions and good detail on the recharge.

I'll give it a try.

Good luck, give it a try, it's fun and satisfying to do this stuff yourself.

And don't forget about using a black light to look for leaks. You can buy a cheap one on Amazon.

[jdecris]

I replaced an older Grunert refrigeration system with three Seafrost BDXP systems in a '91 Grand Banks 46. Two refrigerators and one freezer.

I'm fairly hands on. Rewired the entire Heavy DC system and installed Lifeline batteries - 4Ds and Group 31 start batteries, and a house bank of 6V golfcart batteries, Victron Inverter Charger, ACRs, alternators, regulators. Downsized the top loading freezer with rigid insulation and panels, and installed all three Seafrost systems. Rebuilt the Vacuflush toilet and Groco potable water systems. All brightwork, clean and wax. Etc., etc.

For what it's worth... I've concluded... after many tries to fix... that refrigeration requires a level of knowledge, experience, and tooling that I don't have - and am not interested in pursuing. Too involved. And I have enough to do already.

One of the refrigerator systems was giving me a problem for several seasons - insufficient cooling - and required adding 134A refrigerant. Finally this summer I had a local Marine HVAC tech come on board and troubleshoot and track down the leak. Fixed it, evacuated the system, and added the proper amount / weight of regrigerant. Doing well ever since.

Another poster's statement "... and just top it off..." is not as easy as it sounds. It is however very easy to add too much or too little, and without the proper equipment - gauges, etc. - nearly impossible to get right. Not to mention all the controls, lines, connections for leak potential, etc.

Anyway, my experience and two cents on working on refrigeration.

Good luck with your refrigeration system.

[dougtheslug]

Before you try any recharging or other things, please try this first: Run a decent power wire from your battery to the compressor.

I had the exact same problem (cycling, cooled things to some degree) and the issue was the wiring.

This is because the fridge need a large amount of current to start the electric compressor right at first, and then less once things are up and running. If the compressor doesn't get all the current it needs, which can be stifled by old wires, crappy connections along the way, or simply long wires, the compressor shuts off. Then it tries to start again. Shuts off, starts, etc.